Electrical apparatus



Sept. 25, 1956 E. K. HODSON ELECTRICAL APPARATUS Filed Aug. 15, 1955 FIG. I 5

7 BI'METAL INVENTOR ERNEST K. HODSON ATTORNEYS United States Patent ELECTRICAL APPARATUS Ernest K. Hodson, Caldwell, Idaho Application August 15, 1955, Serial No. 528,325

6 Claims. (Cl. 200-122) This invention relates to a thermal interrupter of the thermal flasher type which may be used to control any external circuit so as to energize and de-energize the circuit intermittently. As a preferred application, an electric fence circuit is disclosed. Such a circuit should be interrupted or chopped cyclically to permit a shocked animal to withdraw in safety. If, however, an interrupter of the more common type be so used and the heater resistance for the bimetal in the interrupter becomes defective as by a short or ground therein, .the fence circuit will remain closed and cause injury to any shocked animal because the shock will be continuous.

Patent No. 2,697,152, issued December 14, 1954, to the present applicant discloses a thermal interrupter and circuit which goes open on the safe side in the event that the interrupter should become defective as just described.

The present application discloses an interrupter that embodies improvements over said patented interrupter in that it is more simple, easier to assemble and less expensive to manufacture.

The main object of this invention is to provide a thermal interrupter wherein but a single bimetallic reed is associated with a metallic reed, the free floating adjacent ends of said reeds carrying a pair of main contactors, in combination with a stationary auxiliary blocking or back contactor that functions to engage the floating end of the metallic reed thereby to limit its further motion and permit the main contactors to open and close cyclically while the external circuit remains closed at said auxiliary contact or to permit energization of a circuit connected thereto.

In the accompanying drawings:

Figure 1 shows, in side elevation partly in section, the complete flasher unit;

Figure 2 shows the thermal flasher as embodied in an external work circuit the load circuit of which is to be intermittently energized; and,

Figure 3 shows an enlarged view, partly in section, of a contact or bushing shown in Figure 1.

In detail, a bimetal reed 1 and a spring type reed 2 are mounted upon a vertical standard 3 that has a laterally extending lug 4 secured thereto. A metallic pin or bolt 5 passes through openings in the upper ends of both reeds and through the lug 4 and standard 3 in a manner to secure these four elements firmly together with the reeds in electrical contact at their upper supported ends. The standard 3 and the lug 4 are formed of non-conducting material such as fiber or a plastic.

The bimetal reed 1 may be heated in the usual manner by a heater 6 which encircles the reed 1 or is positioned close thereto. The lower end of the heater coil 6 is grounded to the bimetal at 7 and the other end thereof is connected to a conductor 8 that leads to a terminal prong 9. A pair of normally closed contactors 10 and 11 are mounted on the free ends, respectively, of the reeds 1 and 2. The contactor 11 is insulated from the reed 2 by means of a fiber bushing 12 which is mounted within an Patented Sept. 25, 1956 opening in that reed. The contactor 11 has an integral pin 13 that extends centrally through the bushing 12 and through a fiber washer 14. A metallic washer 15 surrounds pin 13 and the end of this pin is beaded over to compress these elements. The washer 15 is connected through a conductor 16 to a prong 17.

As shown in Figure 1, in normal unheated position, the bimetal 1 causes its contactor 10 to press forcibly against the contactor 11 and the reed 2 to retain the free end of this reed spaced from the head 18 of an adjustable bolt 19 which is threadably engaged within the standard 3. This bolt is also engaged within a threaded opening in a metallic plate 20 which is connected by conductor 21 to a terminal prong 22.

The standard 3 and the prongs 9, 17, and 22 are mounted on a non-conducting base 23. A cylindrical housing 24 detachably engages the base 23.

Figure 2 shows the interrupter unit positioned within the casing 24. The source of power 25 is connected through conductor 28 to prong 9 and through conductor 26 and switch 27 to prong 17. The primary P of transformer T is shunted across prong 22 and power line 28 through conductor 31. A signal 29 and resistance 30 may be included, if desired. One side of secondary S is connected through conductor 32 and resistance 33 to a terminal 34 and through an alternate path to a terminal 37. An electric fence 35 may be connected through switch 36 to either of terminals 34 or 37. When connected through resistance 33, the shock current take-off from the fence will be reduced by resistance 33. The other side of secondary S is connected through conductor 38 to ground and through signal 39, if desired. Conductors 26 and 28 may be grounded for safety through condensers 40 and 41.

In operation, with switch 27 open, contactors 1011 are closed. Reed 1 is stiffer than reed 2 which causes the free end of the latter to swing away from contact head 18. With switch 27 closed, bimetal reed 1 will be heated by heater 6 since terminal prongs 9 and 17 are now hot. Reeds 1 and 2 will start to move upwardly in unison, contactors 10-11 remaining closed, until the free end of reed 2 contacts head 18. Thereafter, contactors 10-11 start to cycle to open and closed positions though reed 2 remains against head 18. Each time contactors 10-11 close, heater 6 is energized through the lines 26 and 16, contactors 1011, heater 6, line 8 and back to line 28. Reed 2 and head 18 now being in a closed circuit, the current which came from lines 16 and 26 will divide at the grounded end of heater 6 and part of same will traverse the circuit including bimetal 1, reed 2, head 18, line 31, primary P and back through line 28. If the excitation cycle is say five seconds, secondary S will excite fence 35' for five seconds. When contactors 10-11 open, heater 6 is in open circuit as is the alternate path from bimetal 1 through primary P. When the bimetal cools, this alternate circuit will again become energized as contactors 10-11 close.

Obviously, if heater 6 becomes defective, as by an open circuit or a ground therein, contactors 10-11 will remain closed with the contact at head 18 open and primary P remains de-energized. Only when contactors 10-11 are closed and with the heater operative does the primary P become energized.

The main function of making the bolt 19 adjustable is to permit a setting of reed 2 that will avoid soft or dragging contactor operation as well as to permit alteration of open and closed periods.

The following claims are made:

1. A thermal interrupter comprising a bimetal reed and a spring metal reed, means to support and secure the reeds in electrical contact at a pair of ends thereof,

the reeds being spaced apart at their free ends, a first contact on the free end of one reed extending laterally a sutficient distance to engage the other reed and maintain the free reed ends distorted relatively away from each other, a heating element on the bimetal reed, a second contact positioned between the reeds a predetermined distance from the spring reed to permit the latter to move in unison with the bimetal reed when the latter is distorted by heat, said second contact being operative to block further motion of the spring reed and to permit the. bimetal reed to move further to disengage from the first contact, said second contact being adapted to be included in series with an external work circuit with the result that, in the event the heating element becomes, defective, the bimetal reed will cool and flex to re-engage the first contact and disengage the spring reed from the second contact to open the external circuit.

2. In an interrupter as set forth in claim 1, wherein the second contact is associated with means to adjust the same to vary the point at which the spring reed contact will be disengaged from the bimetal reed.

3. In an interrupter as setforth in claim 1-, wherein one end of the heating elementis grounded to the bimetal, means to insulate the spring reed from the contact thereon, a plurality of terminals, conductors extending from one terminal to one of said reeds and from a second terminal to the first contact, whereby, when the spring reed engages the second contact and the first contact is closed against the bimetal reed, the current passing through the heating element will divide to permit a part thereof to flow through the first contact and the other part thereof to flow from the spring reed to the second contact, the latter contact being connected to another one of said plurality of terminals.

4. In an interrupter as set forth in claim 1, wherein the spring reed is more flexible than the bimetal reed;

whereby movement of the latter reed to its extreme cooled position and while it engages the first contact, will move the spring reed an equal amount to cause the latter reed to disengage from the second contact.

5. A thermal interrupter comprising a spring metal reed and a bimetal reed, means to support and secure the reeds in electrical contact at a corresponding pair of ends, a

. pair of normally closed contacts mounted one on each adjacent free reed. end, the free ends of the reeds being relatively distorted from each other a predetermined distance by pressure between said contacts, means to insulate the. spring reed from the contact thereon, a heater resistance mounted on the bimetal reed, one end thereof being grounded to its associatedv reed, a third contact positioned between the reeds, said reeds being movable in unison during heating of the resistance until the spring reed engages the third contact to, thereafter, permit separation of the pair of contacts, a source of power in series circuit with said pair of contacts, said reeds and said. re sistance operative to cause the latter contacts to open and close cyclically while the spring reed engages the third contact.

61. In. an interrupter as set forth in claim 5, an external circuit adapted to be intermittently interrupted and being connected at one end to the third contact and at its other end to one of said, reeds whereby, during closure of the pair of contacts, current will be diverted from said lastnamed reed and through. said circuit.

References Cited in the file of this patent UNITED STATES PATENTS 1,850,206 Hertzberg- Mar. 22, 1932 2,329,119 Jacobs Sept. 7, 1943 2,499,208 Zimmer Feb. 28, 1950 2,697,152 Hodson Dec. 14, 1954 

